The present invention broadly relates to product stacking apparatuses and, more particularly, concerns a new and improved construction of stacking apparatus for stacking or piling printed products, especially printed products arriving in an imbricated or shingled formation. The present invention also relates to an improved method of stacking or piling such printed products.
Generally speaking, the stacking or stacker apparatus for stacking or piling printed products, especially printed products arriving in an imbricated or shingled formation, such as newspapers, periodicals, magazines and the like, is of the type comprising at least one stack former, in particular at least one stacker or stack chute provided with an elevationally displaceable stacker or stack table. There is also provided at least one infeed device arranged upstream or ahead of the stacker chute as viewed with respect to a predetermined direction of travel or infeed of the printed products. This infeed device is pivotable about a pivot axis or shaft arranged at a starting or inlet or infeed region of such infeed device. In an operating position of this infeed device, the latter bears at the region of an end of such infeed device, particularly the product outfeed or outlet end region opening directly into the stacker chute upon the product stack which is to be formed.
Such type of stacking or stacker apparatus is known in this technology from German Published Patent No. 1,436,495, published Jan. 23, 1969. Such prior art stacking apparatus comprises a stacker chute containing an elevationally displaceable stacker table. The product infeed device is arranged upstream of the stacker table. Such product infeed device is mounted to be pivotable about a pivot axis arranged at the starting region of the product infeed device. When the product infeed device assumes its operating or working position, the end region of such product infeed device and which opens into the stacker chute bears upon the product stack which is to be formed. For this purpose, the product infeed device contains an arm member which protrudes past the downstream end of the product infeed device and at which there is arranged a rotatably driven wheel or roll serving to support the product infeed device and at the same time to convey the infed printed products against a stop or impact member. During the stack formation the stacker table is located in its upper terminal position and the product infeed device accommodates itself to the momentarily or currently prevailing stack height by pivoting about its pivot axis. As soon as sufficient printed products have been stacked, then the further infeed of the printed products is interrupted and the product infeed device, while in its upper terminal position, is pivoted or rocked. The stacker table is lowered and the product stack is deposited upon a belt conveyor which outfeeds the product stack in the same direction as the products were infed. Then the stacker table is again raised and the product infeed device is lowered in order to form a new product stack. As a general rule, such product stacks possess a relatively poor stack stability, particularly when the product stack is formed of folded printed products. This is so, because the printed products at the region of the product fold, possess a greater thickness than at the marginal or edge region which is situated opposite the product fold. Thus, the permissible product stack height is appreciably limited.
A stacking or stacker apparatus equipped with two stacker chutes has been disclosed, for instance, in the German Published Patent Application No. 2,752,513, published Apr. 26, 1979 and the cognate British Patent No. 1,568,752, published June 4, 1980. With such prior art stacking apparatus, each stacker chute has arranged upstream thereof a partial stack formation device and such again has associated therewith a product infeed device which is fixedly arranged in a frame. The stacker chutes are separated by slides from the associated partial stack formation devices. The printed products infed in an imbricated product stream or formation arrive by means of a further conveyor arranged upstream of the product infeed device at such product infeed device and are transported by such product infeed device to the partial stack formation device.
The printed products, while being confined by boundary ledges, fall within the confines of the boundary ledges upon the slides or else upon printed products which have already been deposited upon such slides. As soon as a sufficient number of product copies of the printed products are available at a partial stack then by opening the slides the formed partial stack falls onto an elevationally displaceable stacker table or upon a further partial stack already located upon such stacker table. On the other hand, the printed products of the incoming imbricated stream or formation are delivered to the partial stack forming device which is operatively associated with the second stacker chute. After lowering of the stacker table, the slides are placed in their closed position so that the partial stack formation device is ready to receive further printed products. To ensure for a crosswise stacking of the partial stacks, the stacker table together with the partial stack reposing thereupon, is rotated through an angle of about 180.degree. about a vertical axis and, if desired, raised against the slides in order to press or compact the partial stack and thereafter again slightly lowered. In this way, a partial stack is alternately formed in each of both partial stack formation devices and the partial stacks in the associated stacker chute are each deposited in a crosswise posture or configuration upon the related stacker table. As soon as the partial stack within a stacker chute has attained a desired total product stack height, then the stacker table is completely lowered and the product package formed of crosswise superimposed partial stacks is ejected by an ejector device or ejector as the same has been disclosed, for instance, in Swiss Patent No. 623,287 and the corresponding U.S. Pat. No. 4,229,134, granted Oct. 21, 1980.